Operator internet protocol (IP)-enabled set top box (STB) solutions are moving to provide whole-home IP-STB solutions. In these solutions, hub STBs are typically expected to have multiple bridged home networking interfaces. Multiple bridged interfaces provide additional communications options, including bridging of traffic between interfaces for client STBs when needed.
FIG. 1, for example, is a block diagram illustrating one embodiment of a home network 100. The home network 100 may be configured, for example, to provide cable, off-air and Internet-based services to a home user. The home network 100 includes a plurality of terminals 102, 104 and 106 that share content via a plurality of physical (e.g., Ethernet) links 108 and logical (e.g., HomePlug AV (HPAV) or Multimedia over Coax Alliance (MoCA)) links 1101-110n (hereinafter collectively referred to as “logical links 110”). The terminals include one or more home routers 102, one or more hubs 1041-104n (hereinafter referred to as “hubs 104”) and one or more clients 106. Embodiments of hubs 104 may include, for example, tuners, off-air and cable interfaces and/or hard disks for receiving off-air and cable television, digital video recorder (DVR) and Internet content services. Embodiments of clients 106 may be configured as thin clients that receive streaming content from hubs 104. In addition, hubs 104 may stream content to each other. Other embodiments of clients 106 may contain tuners for off-air and/or cable input for streaming received content to a DVR in a hub 104 and receiving the streamed content back for “trick play” service.
With hubs that contain multiple home networking interfaces, it is increasingly likely that a user will create problematic home networking architectures (at or after installation) in which more than one active communication link exists between a hub and another device. For example, in FIG. 1, two links (i.e., 108 and 1101) exist between the router 102 and the hub 1041. If the other device to which the hub is linked is a home router, a switch or another hub, a layer-2 loop can form (wherein packets cycle repeatedly through a constant series of terminals), resulting in degraded performance of the home network due to, for example, inefficient use of resources, flooding of the network with redundant information, wasted bandwidth, and the like. This happens because layer-2 bridges/switches used in home networks (such as envisioned for STB hubs) are simple learning bridges that forward received data frames (layer-2 packets) with broadcast-destination addresses out all interfaces other than the one from which a broadcast data frame is received.
In the example of FIG. 1, layer-2 looping will occur after transmission of a broadcast frame (e.g., Dynamic Host Configuration Protocol (DHCP) discover, Address Resolution Protocol (ARP) request, Universal Plug and Play (UPnP) or Simple Service Discovery (SSDP) search request, presence announcement) from the home router 102 or hub 1041. Those skilled in the art will appreciate that looping can occur in other architectural configurations and between other combinations of terminals, and the architecture illustrated in FIG. 1 is merely one illustrative example.
One method for mitigating layer-2 looping involves adding Institute of Electrical and Electronics Engineers (IEEE) 802.1d standard spanning tree functionality to a hub STB bridge. However, this would only prevent frame looping if the home router's local area network (LAN)-side switch also supported IEEE 802.1d spanning trees, and no such home routers or plans for such home routers are known at this time.
Therefore, there is a need in the art for a method and apparatus for mitigating layer-2 looping in home networking applications that does not rely on IEEE 802.1d spanning tree functionality.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.